Calories In, Calories Out: The Formula and How to Use It for Fat Loss

Calories in, calories out means you lose weight when you eat fewer calories than you burn. A simple starting point: women multiply body weight in pounds by 12 to 14, men by 14 to 16, to estimate maintenance. Subtract 300 to 500 calories for fat loss. Then adjust every two to three weeks based on results.

Is calories in, calories out true?

Yes. Body weight follows energy balance: the energy you take in compared with the energy you use (Hall et al., 2012). What people get wrong is thinking both sides are fixed and easy to measure. They are not. Food labels can be off, fitness trackers often overestimate burn, and your body adjusts a bit as you diet. The formula works. Using it well takes some strategy.

How do I estimate my maintenance calories?

This is the quick version I use to start clients:

• Women: body weight in pounds x 12 to 14
• Men: body weight in pounds x 14 to 16

Use the low end if you sit most of the day and the high end if you are on your feet or train hard several times a week. A 170 pound woman who trains three times a week might start around 170 x 13 = 2,210 calories for maintenance. These are the same starting numbers I use for my Anti-Mom Bod and Anti-Dad Bod clients.

If you want a more detailed estimate, the NIH Body Weight Planner uses research models and accounts for activity and how your body adapts over time.

How big should my calorie deficit be?

For most people, 300 to 500 calories below maintenance. That usually produces about 0.5 to 1 pound of loss per week, which is fast enough to stay motivated and slow enough to keep muscle and sanity.

• If you are lean already, stay closer to 300.
• If you have more weight to lose, 500 is a fine start.
• Avoid very low calorie diets without medical supervision. They are hard to hold and usually end in a rebound.

What makes up the calories out side?

Four parts:

1. Basal metabolic rate, the energy you burn at rest. This is the biggest chunk.
2. The thermic effect of food, the energy used to digest what you eat. Protein costs the most.
3. Exercise.
4. NEAT, or non-exercise activity thermogenesis. Walking, standing, cleaning, fidgeting, taking the stairs.

NEAT is the one people forget. In an overfeeding study, the difference in daily non-exercise movement between people explained much of why some gained more fat than others (Levine et al., 1999). An hour of training does not make up for sitting the other 15 waking hours.

How do I increase NEAT?

• Aim for 8,000 to 12,000 steps a day.
• Walk during phone calls and after meals.
• Park farther away and take the stairs.
• If you work at a desk, stand or walk for a few minutes every hour.

Why does my fat loss stall on a calorie deficit?

The most common reasons I see:

• Tracking drifts. Weekend meals, cooking oil, drinks and bites while cooking stop getting logged.
• Your burn dropped. As you get lighter, you burn less, and many people move less without noticing (Rosenbaum and Leibel, 2010).
• Water retention from stress, poor sleep, a new training block or your cycle hides fat loss for a week or two.
• The deficit was too aggressive, so hunger wins and you rebound.

If the scale and your waist have not moved in three weeks, tighten tracking first, add steps second and cut 100 to 200 calories third. Some clients do well with a planned maintenance week every couple of months, and one trial found breaks like that made dieting more efficient for men with obesity (Byrne et al., 2018).

Do macros matter if calories are right?

Calories decide how much you lose. Protein decides whether you keep your muscle while you do it. Read should you focus on macros or calories for weight loss and how to figure out your protein needs. If you want me to set your numbers, take the XPL quiz.